1. Field of the Invention
This invention relates to a wrapping machine for packaging or bundling articles, typically in a thermo-shrinkable film.
2. Prior Art
Machines for moving an article or groups of articles through the plane of a continuous film, wrapping the article or articles with the film, sealing the film into a tube, severing the tube and resealing the film, and then shrinking the tube about the article or articles, are exemplified by U.S. Pat. Nos. 3,191,356; 3,357,151; 3,488,912; 3,490,194; 3,552,091; 3,830,036; and 3,869,844. Basically, such machines provide a generally horizontal conveyor for articles and extend a film vertically across the path from supply rolls above and below. An article or group of articles is moved through the plane of the film, which is fed or pulled from the supply rolls so the article or articles to be packaged or wrapped move over a portion of the film fed from below while another portion of the film is drawn from above, over the front and top of the article or group of articles. A moving bar pulls the film from above down behind the article or articles and clamps the film portions from above and below together behind the article or articles to form a tube. The clamped film is sealed across the width of the film along two spaced lines and is severed between the lines. This results in a sealed tube about the article or articles, which is separate from the remaining film, of which the upper and lower portions are sealed into a single web for the next article or group of articles to intercept. The article or articles and tubular wrapping are then moved through a heated environment to shrink the tube.
Many of the machines shown in the prior art or in existence are both expensive and complex. Also, where a variety of product sizes and shapes are to be packaged, a particular machine configuration may be inefficient for some of the sizes or shapes. In addition, with small and lightweight articles, typical conveying approaches are often inadequate to assure movement past the plane of the wrapping film. In particular, with tall articles, known techniques apply excess tension to the film as it is wrapped behind the article, or excess film is used to avoid the tension. Such tension may tip the article or articles, or tear the film. Excess film is of course wasteful and undesirable in the finished package.